Widespread occurrence of spliceosomal introns in the rDNA genes of ascomycetes

Debashish Bhattacharya, François Lutzoni, Valérie Reeb, Dawn Simon, John Nason, Fernando Fernandez

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

Spliceosomal (pre-mRNA) introns have previously been found in eukaryotic protein-coding genes, in the small nuclear RNAs of some fungi, and in the small- and large-subunit ribosomal DNA genes of a limited number of ascomycetes. How the majority of these introns originate remains an open question because few proven cases of recent and pervasive intron origin have been documented. We report here the widespread occurrence of spliceosomal introns (69 introns at 27 different sites) in the small- and large-subunit nuclear-encoded rDNA of lichen-forming and free-living members of the Ascomycota. Our analyses suggest that these spliceosomal introns are of relatively recent origin, i.e., within the Euascomycetes, and have arisen through aberrant reverse-splicing (in trans) of free pre-mRNA introns into rRNAs. The spliceosome itself, and not an external agent (e.g., transposable elements, group II introns), may have given rise to these introns. A nonrandom sequence pattern was found at sites flanking the rRNA spliceosomal introns. This pattern (AG-intron-G) closely resembles the proto-splice site (MAG-intron-R) postulated for intron insertions in pre-mRNA genes. The clustered positions of spliceosomal introns on secondary structures suggest that particular rRNA regions are preferred sites for insertion through reverse-splicing.

Original languageEnglish (US)
Pages (from-to)1971-1984
Number of pages14
JournalMolecular biology and evolution
Volume17
Issue number12
DOIs
StatePublished - Jan 1 2000

Fingerprint

Ascomycota
Ribosomal DNA
Introns
introns
gene
Genes
genes
secondary structure
lichen
RNA
fungus
RNA Precursors
DNA
protein
ribosomal RNA
Trans-Splicing
trans-splicing
spliceosomes
small nuclear RNA
Spliceosomes

Keywords

  • Ascomycetes
  • Group I introns
  • Lichen symbiosis
  • Proto-splice site
  • Reverse-splicing
  • Spliceosomal intron origin
  • rDNA

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics

Cite this

Widespread occurrence of spliceosomal introns in the rDNA genes of ascomycetes. / Bhattacharya, Debashish; Lutzoni, François; Reeb, Valérie; Simon, Dawn; Nason, John; Fernandez, Fernando.

In: Molecular biology and evolution, Vol. 17, No. 12, 01.01.2000, p. 1971-1984.

Research output: Contribution to journalArticle

Bhattacharya, Debashish ; Lutzoni, François ; Reeb, Valérie ; Simon, Dawn ; Nason, John ; Fernandez, Fernando. / Widespread occurrence of spliceosomal introns in the rDNA genes of ascomycetes. In: Molecular biology and evolution. 2000 ; Vol. 17, No. 12. pp. 1971-1984.
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